Truck Axle Load Calculation Example: How Body Position Changes Axle Loads
An axle-load calculation predicts how the mass and position of a truck body, crane, tanks, toolboxes, payload and other equipment will be shared between the axles. It is useful before fabrication because a vehicle can remain under its GVM and still overload an individual axle, tyre or OEM rating.
The example below is educational only. Actual vehicle assessment must use the real vehicle dimensions, tare masses, axle ratings, tyre capacities, equipment data and applicable legal mass limits.
Illustrative two-axle rigid truck
- Wheelbase: 4.50 m.
- Base tare front axle: 3,000 kg.
- Base tare rear axle: 2,500 kg.
- Illustrative front axle rating: 5,500 kg.
- Illustrative rear axle rating: 8,000 kg.
- Illustrative GVM: 12,000 kg.
Add a 1,500 kg body
Assume the body’s centre of gravity is 2.80 m behind the front axle. Using the wheelbase as the support spacing, the rear-axle reaction from the body is approximately 933 kg and the front-axle reaction is approximately 567 kg.
Add an 800 kg crane
If the crane centre of gravity is 4.00 m behind the front axle, it contributes approximately 711 kg to the rear axle and 89 kg to the front axle.
Add a 4,000 kg payload
If the payload centre of gravity is 3.20 m behind the front axle, it contributes approximately 2,844 kg to the rear axle and 1,156 kg to the front axle.
How the calculation works
For an added mass, its rear-axle contribution equals the mass multiplied by its centre-of-gravity distance behind the front axle, divided by the wheelbase. Its front-axle contribution equals the added mass minus the rear-axle contribution. Add these contributions to the measured base tare axle masses.
For the body: 1,500 × 2.80 ÷ 4.50 = 933.33 kg on the rear axle. The front contribution is 1,500 − 933.33 = 566.67 kg. These are static mass-equivalent axle loads, not dynamic loading or structural design forces.
Resulting illustrative axle loads
Individual contributions are rounded to the nearest kilogram for display. Totals are calculated using unrounded contributions, then rounded, so the displayed rows may differ from the totals by 1 kg.
| Item | Front axle contribution | Rear axle contribution |
|---|---|---|
| Base vehicle tare | 3,000 kg | 2,500 kg |
| 1,500 kg body | 567 kg | 933 kg |
| 800 kg crane | 89 kg | 711 kg |
| 4,000 kg payload | 1,156 kg | 2,844 kg |
| Total (rounded) | 4,811 kg | 6,989 kg |
The total vehicle mass in this example is 11,800 kg. That is below the illustrative 12,000 kg GVM, and both axle loads are below the example axle ratings. A real engineering assessment would also check applicable legal axle-group limits, tyre capacities and any OEM restrictions.
What happens if the crane moves rearward?
Moving concentrated equipment rearward increases its rear-axle reaction and can reduce the load on the front axle. If the same 800 kg crane centre of gravity moves from 4.00 m to 5.20 m behind the front axle, its illustrative contribution becomes approximately 924 kg on the rear axle and minus 124 kg on the front axle. This demonstrates why equipment position can materially change axle loading even though the equipment mass has not changed.
Why GVM alone is not enough
A vehicle can be below its GVM but still exceed a front or rear axle rating. The configuration also needs to be checked against the applicable legal mass limits, OEM axle ratings, tyre capacities and any other relevant vehicle limits.
What CVC considers in an axle-load configuration
- Wheelbase and axle locations.
- Base tare and known axle masses.
- Body mass and centre of gravity.
- Cranes, hooklifts, tanks, toolboxes, tailgates and other equipment.
- Payload magnitude and load position.
- Rear overhang and body position.
- OEM ratings and applicable legal mass limits.
- Alternative wheelbases or equipment positions where comparison is required.
Use the calculation before fabrication
For body builders and manufacturers, the greatest value is often at the design stage. Axle-load calculations can help select a wheelbase, body position or equipment location before fabrication starts, reducing the risk that a completed vehicle needs expensive repositioning or redesign.
Related CVC engineering services
- Truck Axle Load Calculations
- Truck Cranes, Tippers, Hooklifts & Tow Couplings
- Commercial Vehicle Engineering for Body Builders
Need an axle-load calculation for a real vehicle?
Submit the vehicle and proposed configuration to CVC for a vehicle-specific engineering axle-load assessment.
Technical content reviewed by Darren Ludecke, Managing Director | AVE | VASS Signatory. Updated September 2026.